The conventional technology will be explained using the cleaning process of an LSI process as an example.
In an LSI manufacturing process, an oxide film is formed on a silicon wafer, window-opening having a predetermined pattern is conducted in the oxide film, and then cleaning is conducted, and depending on the purpose, p-type or n-type chemical elements are introduced, and a procedure, in which the above impurities are diffused or annealed in the silicon, is repeatedly conducted in a thermal diffusion furnace, and elements are thus formed.
When conducting heat treatment such as thermal diffusion or annealing or the like, if even a small amount of impurities such as, for example, metals or the like, adhere to the silicon surface, then the characteristics of the element which is formed worsen; for example, a drop in the base collector withstand voltage, an increase in leak currents, or the like, is experienced.
Accordingly, in semiconductor manufacturing processes, cleaning processes are extremely important in order to manufacture high-performance elements, and it is necessary to completely remove the contaminants on the silicon.
However, after the removal of an oxide film, the silicon surface is hydrophobic, and the wettability thereof with water is normally poor, so that, in other words, it is difficult to bring the pure water and the contaminant impurities into contact, and it is difficult to completely clean away the very small amount of impurities adhering to the silicon surface. As a result, it is impossible to obtain elements having higher performance, as explained above, and this represents a great hindrance to the attainment of a shift to high performance elements.
The present invention has as an object thereof to provide a method of and system for producing pure water which is capable of completely cleaning away impurities on silicon by improving the wettability with pure water of a substrate body surface, and in particular, a silicon wafer substrate body from which an oxide film has been removed, and bringing pure water into contact with the silicon surface, and to provide a cleaning method.